The present invention relates to a method for baking a semiconductor device that has a semiconductor element and a resin encapsulated package.
Semiconductor devices such as a transistor, an integrated circuit (IC) and a large scale integrated circuit (LSI) are each encapsulated in a ceramic package, a plastic package or the like. The plastic package is going mainstream, except for particular specifications, since it is especially excellent in terms of cost and productivity.
FIG. 2 is a schematic sectional view of a semiconductor device that has a plastic package of the thin small outline package (TSOP) type or the like. This semiconductor device 100 shown in FIG. 2 has assembly processes as follows.
First of all, a die bonding paste containing an organic solvent is coated on a frame 101 made of alloy, and a semiconductor chip 102 bis die-bonded onto the frame 101.
Next, the semiconductor chip 102 and the frame 101 are subjected to a heating process in an N2 atmosphere by means of an oven and thereafter to a wire bonding process to connect the semiconductor chip 102 with lead terminals 103 and 103 by way of Au wires 106 and 106.
Next, before performing resin encapsulation, a polyimide based resin (PIQ) film 104 is formed on a surface of the frame 101 opposite to the semiconductor chip 102 in order to secure adhesion of the frame 101 to a plastic package 105. Thereafter, the PIQ film 104 is subjected to a heating process for hardening it.
Next, resin is molded into the package 105 of the TSOP type by a molding press after completing the heating process of the PIQ film 104, and then the package 105 of the TSOP type is subjected to a heating process in a N2 atmosphere.
Next, the lead terminals 103 and 103 are formed, subjected to a plating process, and followed by a baking process.
In a conventional baking method of a semiconductor device, moisture absorbed in the plastic package 105 and organic components contained in the plastic package 105 are removed by subjecting the semiconductor device 100 to the baking process at a temperature 150xc2x0 C. for one hour in a N2 atmosphere at the atmospheric pressure.
However, the aforementioned semiconductor device baking method is not able to sufficiently remove the organic components contained in the plastic package 105. Consequently, if a reflow process is performed at a temperature of e.g. 230xc2x0 C. for three minutes to connect the semiconductor device 100 to a circuit substrate, there occurs a problem that a blister 105a shown in FIG. 3 or cracks are generated in the plastic package 105.
Accordingly, the present invention has an object of providing a semiconductor device baking method capable of preventing deformation such as blisters and cracks of a plastic package.
In order to achieve the aforementioned object, the present invention provides a semiconductor device baking method for baking a semiconductor device that has a semiconductor element and a resin encapsulated package, comprising the steps of: encapsulating the semiconductor element with resin into the resin encapsulated package; and baking the resin encapsulated package in a reduced-pressure atmosphere.
According to the present invention, it has been found that moisture and organic components inside the resin encapsulated package are easily discharged out of the resin encapsulated package by baking the resin encapsulated package in the reduced-pressure atmosphere. As a result, the moisture and the organic components inside the resin encapsulated package are sufficiently reduced, so that the resin encapsulated package can be prevented from deformation such as blisters and cracks in, for example, the reflow process after the baking process.
In one embodiment of the present invention, the reduced-pressure atmosphere is an atmosphere having a vacuum degree of 10xe2x88x926 torr or less.
According to the above embodiment, deformation such as blisters and cracks in the resin encapsulated package can more reliably be prevented by setting the reduced-pressure atmosphere to 10xe2x88x926 torr or less.
If the reduced-pressure atmosphere is greater than the value of 10xe2x88x926 torr, the moisture and the organic components inside the resin encapsulated package are insufficiently removed.
In one embodiment of the present invention, the resin encapsulated package is heated within a temperature range of 165xc2x0 C. to 175xc2x0 C. in the step of baking the resin encapsulated package.
According to the above embodiment, deformation such as blisters and cracks in the resin encapsulated package can more reliably be prevented by baking the resin encapsulated package within the temperature range of 165xc2x0 C. to 175xc2x0 C.
If the baking is performed at a temperature lower than 165xc2x0 C., the moisture and the organic components inside the resin encapsulated package are insufficiently removed.
If the baking process temperature exceeds 175xc2x0 C., the resin encapsulated package suffers heat damages.
In one embodiment of the present invention, the resin encapsulated package is heated for 6 hours or more in the step of baking the resin encapsulated package.
According to the above embodiment of the present invention, the deformation such as blisters and cracks in the resin encapsulated package can more reliably be prevented by heating the resin encapsulated package for 6 hours or more.
If the heating time of the resin encapsulated package is less than 6 hours, the moisture and the organic components inside the resin encapsulated package are insufficiently removed.
In one embodiment of the present invention, the resin encapsulated package belongs to a TSOP type.
According to the above embodiment of the present invention, deformation such as blisters and cracks in the resin encapsulated package can effectively be prevented since the resin encapsulated package belongs to the TSOP type.